Retinal vein occlusion is a medical condition where there is a blockage
in the retinal veins. This blocks the flow of blood in the retina, which
can damage the nerve cells of the eye and result in loss of vision.
Retinal vein occlusion can occur as a result of a clot in a vein,
especially if the veins of the eye are very narrow. The disease is
likely to affect people who are already suffering from hypertension,
diabetes mellitus, or hyperlipidaemia.

Retinal vein occlusion is one of the most common causes of blindness
after diabetic retinopathy. It is lso one of the most common vascular
disorders of the eye. Retinal vein occlusion can be broadly classified
into two types, central retinal vein occlusion and branch retinal vein
occlusion, with the latter being more frequent. Central retinal vein
occlusion can be divided into two further subtypes, ischemic central
retinal vein occlusion and non-ischemic central retinal vein occlusion.